Riser clamp



FIG. 1 is a top perspective view of the riser clamp;

FIG. 2 is a bottom perspective view of the riser clamp;

FIG. 3 is a front elevation view of the riser clamp;

FIG. 4 is a rear elevation view of the riser clamp;

FIG. 5 is a left side elevation view of the riser clamp;

FIG. 6 is a right side elevation view of the riser clamp;

FIG. 7 is a top plan view of the riser clamp; and,

FIG. 8 is a bottom plan view of the riser clamp. 

CLAIM The ornamental design for a riser clamp, as shown and described. 